FILE – In this Jan. 20, 2011, file photo, an American Eagle jet taxis at Boston’s Logan International Airport. The Transportation Department announced Monday, Nov. 14, that they are fining the regional affiliate of American Airlines $900,000 for keeping passengers cooped up on planes for over three hours in Chicago at O’Hare International Airport earlier this year.

American Eagle regional airline agreed to pay $900,000 for stranding passengers on 15 planes for more than three hours on Memorial Day weekend, the first penalty levied under the U.S. tarmac-delay rule.

The delays at Chicago’s O’Hare International Airport affected 608 passengers. American Eagle was late in using a procedure developed to bring travelers to the gate, the Transportation Department said in a statement.

“We put the tarmac rule in place to protect passengers, and we take any violation very seriously,” said Transportation Secretary Ray LaHood. “We will work to ensure that airlines and airports coordinate their resources and plans to avoid keeping passengers delayed on the tarmac.”

The department is investigating incidents Oct. 29 at Bradley International Airport near Hartford, Conn., in which JetBlue stranded passengers on planes for as long as 7 1/2 hours during a snowstorm. Bloomberg News